In this paper I look at two connections between natural philosophy and theology in the late 17th century. In the last quarter of the century there was an interesting development of an argument, earlier but sketchier versions of which can be found in classical philosophers and in Descartes. The manoeuvre in question goes like this: first, prove that there must, necessarily, be a being which is, in some sense of "greater", greater than humans. Second, sketch a proof that such a being is necessary. Move from the fact that there must be at least one such being to the conclusion that there is precisely one such being. Raise the question: could this necessary being be matter, the entire material universe, or must it be God? Produce an argument from natural philosophy to show that matter cannot be the required necessary being. Either explicitly or implicitly run the obvious disjunctive syllogism and conclude with a few remarks about the foolishness of atheism. The argument, which has classical roots, found a number of 17th-century exponents. Cudworth provided the most important version, and Locke, Bentley and Clarke adapted Cudworth's version with varying success. The argument touches on natural philosophy in two ways. First, the basis of the argument invites consideration of a problem in the philosophy of science - the relation between micro properties and macro properties - which was seen clearly enough in some contexts but which was overlooked in others, particularly when the theological aspect was uppermost. The second point of contact involves a direct application of a scientific result - the existence of a vacuum - to the theological issue.